Circuit testing is an important part of circuit development. There are many instruments that are available to perform the testing function, including digital multimeters, oscilloscopes and logic analyzers. With product development and introduction cycles becoming shorter, finding faults earlier in the system design and manufacturing stages is paramount.
However, "in-house" testing, or testing during design and manufacturing stages, is only one part of circuit testing. Testing of circuits is also required after the product has been sold and installed at customer premises. In such field situations a portable and easily configurable in-circuit test system is required. Typically testing in such situations employs oscilloscopes, logic analyzers, and/or multimeters. These instruments are carried to the laboratory or into the field and are connected to the circuit board via test clips connected to wires attached to the test equipment. One problem with this scenario is that most test equipment is too cumbersome to be carried around for general purpose testing.
Logic analyzers are high speed devices that detect and record logic changes in circuits. These devices are most useful for examining multiple signals simultaneously. A logic analyzer can be, for example, connected to the digital bus of a system to read address information on the bus and provide a digital indication of either or both the address and the information associated with the address. For instance, in a digital system using a microprocessor, various diagnostic system tests can be performed with a logic analyzer intercepting the flow of information within the system. One problem with currently available logic analyzers is that they are large and expensive, especially those that use an oscilloscope to display the encoded information. Another problem is these devices are too sophisticated, and as a result, are too complex and expensive to be used for simple circuit testing.